The invention relates to methods and catalysts for producing alcohols, ethers, and/or alkenes from alkanes. More particularly, the invention relates to a novel caged, or encapsulated, metal oxide catalysts and processes utilizing such catalysts. This invention further relates to a process to convert alkanes to alcohols and/or ethers to alkenes.
Lower alkenes, such as ethylene, propylene and butylene are used for a variety of applications. For example, ethylene is one of the most produced organic compound in the world, with the majority of ethylene being used to produce ethylene oxide, ethylene dichloride, and polyethylene. Lower alkenes may be recovered from petroleum by fractional distillation but demand far exceeds recovery by this method. Therefore, the majority of lower alkenes are produced by energy intensive cracking processes that are well known in the art. For example, ethylene is commonly produced in the petrochemical industry by steam cracking in which gaseous or light liquid hydrocarbons are heated to 700-950° C., in the presence of steam followed by rapid cooling, thereby converting large hydrocarbons into smaller ones and introducing unsaturation. Ethylene is then separated from the resulting product mixture by repeated compression and distillation. More recently, efforts to overcome the energy requirements and other issues, such as CO2 issues, related to steam cracking, have resulted in processes involving catalytic cracking using a fluid-bed catalyst such as those processes described in U.S. Patent Publication No. 20090137857.
Other methods are known for producing alkenes, such as from acid dehydration of alcohols, are also well known. Such methods, however, have heretofore, only been practical in laboratory, and not industrial, settings and quantities. In such laboratory methods, alcohols may be formed by reaction of alkyl halides and metal hydroxides. For example, U.S. Pat. No. 5,334,777 shows the reaction of methyl chloride in the vapor phase with magnesium oxide and with magnesium oxide zeolite. U.S. Pat. No. 3,172,915 discloses the use of ferric oxide as a base to react with methyl chloride to form methyl alcohol, while U.S. Pat. No. 5,998,679 discloses a process in which ferric hydroxide is used as a base to react in the liquid phase with methyl bromide. Finally, U.S. Pat. Nos. 6,462,243; 6,465,696; 6,472,572; 6,486,368; 6,403,840; and 6,525,230 all disclose a process in which alkyl bromides are reacted with a metallic oxide to form alcohols and other products, such as di-methyl ether. All of these processes remain impractical for industrial use due mainly to catalyst attrition and over-halogenation problems resulting in the need for expensive re-crystallation.
There remains a need, therefore, for a process to form alcohol, ether or alkene at commercially practicable rates, with minimization or elimination of formation of other related compounds, and specially higher halides. There is a further need for catalysts to effectuate such process while minimizing or preventing the simultaneous production of higher halides during alcohol or alkene formation.